title: Modulation of visually evoked cortical FMRI responses by phase of ongoing occipital alpha oscillations.
abstract: Using simultaneous electroencephalography as a measure of ongoing activity and functional magnetic resonance imaging (fMRI) as a measure of the stimulus-driven neural response, we examined whether the amplitude and phase of occipital alpha oscillations at the onset of a brief visual stimulus affects the amplitude of the visually evoked fMRI response. When accounting for intrinsic coupling of alpha amplitude and occipital fMRI signal by modeling and subtracting pseudo-trials, no significant effect of prestimulus alpha amplitude on the evoked fMRI response could be demonstrated. Regarding the effect of alpha phase, we found that stimuli arriving at the peak of the alpha cycle yielded a lower blood oxygenation level-dependent (BOLD) fMRI response in early visual cortex (V1/V2) than stimuli presented at the trough of the cycle. Our results therefore show that phase of occipital alpha oscillations impacts the overall strength of a visually evoked response, as indexed by the BOLD signal. This observation complements existing evidence that alpha oscillations reflect periodic variations in cortical excitability and suggests that the phase of oscillations in postsynaptic potentials can serve as a mechanism of gain control for incoming neural activity. Finally, our findings provide a putative neural basis for observations of alpha phase dependence of visual perceptual performance.
authors.affiliation: INSERM Unité 992 Cognitive Neuroimaging, and Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut d'Imagerie Biomédicale, NeuroSpin, F-91191 Gif-sur-Yvette, France. Rene.Scheeringa@gmail.com
authors.forename: René
authors.initials: R
authors.lastname: Scheeringa
authors.forename: Ali
authors.initials: A
authors.lastname: Mazaheri
authors.forename: Ingo
authors.initials: I
authors.lastname: Bojak
authors.forename: David G
authors.initials: DG
authors.lastname: Norris
authors.forename: Andreas
authors.initials: A
authors.lastname: Kleinschmidt
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000513:Alpha Rhythm / Q000502:physiology*; D000704:Analysis of Variance; D001931:Brain Mapping / Q000379:methods*; D002540:Cerebral Cortex / Q000502:physiology*; D004569:Electroencephalography; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology